Reciprocating internal combustion (IC) engines are known for converting chemical energy from a fuel supply into mechanical shaft power. A fuel-oxidizer mixture is received in a variable volume of an IC engine defined by a piston translating within a cylinder bore. The fuel-oxidizer mixture burns inside the variable volume to convert chemical energy in the mixture into heat. In turn, expansion of the combustion products within the variable volume performs work on the piston, which may be transferred to an output shaft of the IC engine.
Some constituents in the exhaust stream from an IC engine, such as, for example, nitrogen oxides (NOx), unburned hydrocarbons (UHCs), and particulate matter (PM), may be subject to government regulations. Accordingly, operators may wish to control concentrations of regulated exhaust constituents released to the environment. The composition of exhaust discharged from an IC engine may be affected by control of the combustion process within the variable volume combustion chamber, exhaust aftertreatment downstream of the combustion chamber, or combinations thereof.
Some IC engines employ an externally-powered ignition source to initiate combustion of the fuel-oxidizer mixture within the variable volume. For example, an IC engine may include a spark plug defining a spark gap between an anode and a cathode, where the spark gap is in fluid communication with the variable volume and in electrical communication with an electric potential. Accordingly, applying the electric potential across the spark gap may cause an electric spark to arc across the spark gap, thereby initiating combustion of the fuel-oxidizer mixture within the variable volume.
Further, recirculation of exhaust gas from the exhaust of an IC engine back to the inlet of the IC engine is known. The recirculated exhaust gas flow may be mixed with a fresh oxidizer flow to vary an oxygen concentration of the oxidizer mixture entering the combustion chamber, a temperature of the oxidizer mixture entering the combustion chamber, or both.
U.S. Pat. No. 3,941,105 (“the '105 patent”), entitled “Exhaust Gas Recirculation for Three-Valve Engine,” purports to address the problem of reducing the amount of nitrogen oxides in the engine exhaust gases discharged to the atmosphere. The '105 patent describes an internal combustion piston engine of the spark-ignition type having a main combustion chamber and an auxiliary combustion chamber connected through a torch nozzle restriction. The auxiliary combustion chamber of the '105 patent is fluidly coupled to an exhaust chamber via a valve.
According to the '105 patent, a rich mixture is ignited in the auxiliary combustion chamber to project a flame through the torch nozzle restriction to ignite a lean mixture in the main combustion chamber. However, ignition of a rich mixture in the auxiliary combustion chamber may not satisfy the needs for emissions control and combustion control in some applications. Furthermore, the '105 patent does not provide guidance on how to operate the internal combustion engine by igniting a lean mixture in the auxiliary combustion chamber.
Accordingly, there is a need for improved ignition apparatus and methods for reciprocating IC engines to address the aforementioned problems and/or other problems in the art.
It will be appreciated that this background description has been created to aid the reader, and is not to be taken as a concession that any of the indicated problems were themselves known previously in the art.